Fix serialization issues exposed by enabling InMemoryConnection to serialize PostData

Author: gmarz

src/Elasticsearch.Net/Connection/InMemoryConnection.cs

@@ -49,7 +49,7 @@ protected ElasticsearchResponse<TReturn> ReturnConnectionStatus<TReturn>(Request
             var builder = new ResponseBuilder<TReturn>(requestData)
 			{
 				StatusCode = statusCode ?? this._statusCode,
-				Stream = (body != null) ? new MemoryStream(body) : null,
+				Stream = (body != null) ? new MemoryStream(body) : null
 			};
 			var cs = builder.ToResponse();
 			return cs;

src/Elasticsearch.Net/Transport/PostData.cs

@@ -45,8 +45,8 @@ public void Write(Stream writableStream, IConnectionConfigurationValues settings
 				case PostType.ByteArray: 
 					ms = new MemoryStream(WrittenBytes);
 					break;
-				case PostType.LiteralString: 
-					ms = new MemoryStream(_literalString?.Utf8Bytes());
+				case PostType.LiteralString:
+					ms = !string.IsNullOrEmpty(_literalString) ? new MemoryStream(_literalString?.Utf8Bytes()) : null;
 					break;
 				case PostType.EnumerableOfString: 
 					ms = _enumurabeOfStrings.HasAny() ? new MemoryStream((string.Join("\n", _enumurabeOfStrings) + "\n").Utf8Bytes()) : null;

src/Nest/Search/Percolator/MultiPercolate/MultiPercolateJsonConverter.cs

@@ -14,6 +14,7 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
 		{
 			var request = value as IMultiPercolateRequest;
 			if (request == null) return;
+			if (request.Percolations == null) return;
 
 			var settings = serializer.GetConnectionSettings();
 			var elasticsearchSerializer = settings.Serializer;

src/Tests/ClientConcepts/LowLevel/PostData.doc.cs

@@ -58,7 +58,7 @@ [U] public void ImplicitConversions()
 			fromListOfObject.Type.Should().Be(PostType.EnumerableOfObject);
 			fromObject.Type.Should().Be(PostType.Serializable);
 
-			//passing a PostData<obkect> object to a method taking PostData<object> should not wrap
+			//passing a PostData<object> object to a method taking PostData<object> should not wrap
 
 			fromString = ImplicitlyConvertsFrom(fromString);
 			fromByteArray = ImplicitlyConvertsFrom(fromByteArray);